postgresql.conf and pg_ctl reload

Hi all,

postgresql.conf says:
# This file is read on postmaster startup and when the postmaster
# receives a SIGHUP. If you edit the file on a running system, you have
# to SIGHUP the postmaster for the changes to take effect, or use
# "pg_ctl reload".

Does that mean I can just use "pg_ctl reload" to let the changed
parameters take affect? Or do I have to restart postgres? Or only some
parameters can be taken affect by "pg_ctl reload" (if this case, what are they)?

Same question from man page of pg_ctl:
pg_ctl reload -
simply sends the postmaster a SIGHUP signal, causing it to reread
its configuration files (postgresql.conf, pg_hba.conf, etc.).
This allows changing of configuration-file options that do not require a
complete restart to take effect.

The problem is which options do not require a complete restart and which ones do?

Thanks,